Baths and processes for the production of metal electroplates



United States Patent 18 Claims. (c1. 204-49 This invention relates to improved brightening additives for electroplating baths and to the electroplating process using these brighteners. It more particularly relates to the use of organic sulfonic acid derivatives in electroplating baths whereby the electroplating process may be operated at higher temperatures.

It is known from German Patent No. 888,493 that electrolyte soluble derivatives of esters of sulfothio or trithiocarbonic acid or of dithiocarbamic acid, which contain the grouping I! cs at least once in the molecule, can be added to copper electroplating baths of customary compositions in order to achieve an improved brightening effect on the objects to be copper electroplated. The solubilizing group, a carboxyl or sulfonic acid group, in these derivatives is attached to the sulfur atom of the s ll C S grouping through a short chain bivalent aliphatic radical. At bath temperatures up to about 30 C., these additives exhibit an excellent brightening effect, but their leveling effect is not always completely satisfactory.

It is an object of this invention to provide an electroplating bath and process for obtaining bright and level electrodeposits of metals.

A further object of this invention is to provide an electroplating process and bath operable at higher tem peratures.

Another object is to provide additives for electroplating baths which give both a brightening and a leveling etfect.

These and other objects of my invention will become apparent as the description thereof proceeds.

hydrogen. In the event that R represents an aliphatic radical, the substituents R and K" may also form a ring system together with the nitrogen atom, which may contain a further heteroatom.

Compounds of this type are obtained in known fashion, -for example, by reaction of dithiocarbamates with tolyls-ultone (inner ester of O-oxymethyl sulfon-ic acid), correspondingly substituted tolyl sultones or halogen-alkylaryl sulfonates. The latter are accessible through halogenation of alkylaryl sult'onates, for instances, in suspension in a high-boiling point inert solvent which is inert toward halogen or by treatment of the halogen al-kyl aromates with chlorosulfonic acids at C. or with thionyl chloride; in the last case a hydrolysis of the sulfochloride to form sulfonic acid must be excluded. The

. following are a few examples of salts of such aromatic We have now found that it is possible to obtain full grouping through a bivalent hydrocarbon radical which contains an aryl group. Compounds of the type contemplated in accordance with the invention are characterized by the following general formula:

In this formula R represents an aliphatic, cycloaliphatic or aromatic hydrocarbon radical, X is a heteroatom such as oxygen, NR (-R='I-I or R) or S, R is a bivalent hydrocarbon radical, which contains an -aryl group, and G is a cation of an inorganic or organic base or also su-lfonic acids which contain alkyl radicals and which may be used as bright electroplating additives in accordance with the present invention:

N,N-diethyl-dithiocarbamic acid S benzylester-o-sodium sulfonate,

N-butyl-dithiocarbatnic acid-S-benzylester-psodium sulfonate,

S-phenyl-trithiocarbonate acid S-benylester-o-sodium sulfonate,

N,N-l,S-pentamethylene-dithiocarbamic acid-S- benzylester-o-sodium sulfionate,

N,N-1,S-pentamethylene-dithiocarbamic acid-S-(mmethyl)benzylester-sodium sulfonate,

3-oxa-N,N-1,5pentamethylene-dithiocarbamic acid-S- (p-methyl)2-phenylethylester-sodium sulfonate,

S-phenyl-trit-hiocarb-onic acid-S-(3,5-dimcthyl) benzylester sodium sulfonate,

n-Butyl-xanthogenic acid-S-naphthyl-methyl ester sodium sulfonate,

the reaction product of diethyl dithio carbamate and tetrapropylene benzene sodium sulf-onate which is halogenated in the carbon chain, and the like.

The electroplating additives according to the present invention may be employed in all types of electroplating processes, especially for copper plating, nickel plating, silver plating, zinc plating, as well as for the preparation of cadmium, bronze or brass electroplates. These agents may also be employed in conjunction with other known brightening agents as Well as with leveling agents, porosity prevention agents, hardness binding agents, inhibitors, wetting agents, conductive salts, etc.

The amounts in which the agents according to the present invention, are added to the baths lie between about 0.01 to 20 g./l. of bath fluid. In general, the baths are operated at current densities between 0.5 and 12 amperes per dm. and in special cases at temperatures up to 70 C. It should be particularly emphasized that in the case of an acid copper electroplating bath, the bath containing the agents according to the present invention may be operated within a temperature range of 15 to 50 C., and under these conditions the bath produces complete mirror brightening elfects and the leveling efiect of the baths as a rule completely satisfies the practical requirements.

The base metal to be electroplated may be any type of metal previously employed for this purpose, such as iron, steel, zinc, and other non-precious metals or metal alloys. If necessary, in conjunction with the copper electroplating of non-precious metals, the base metal is as usual provided with .a' thin preliminary copper plate in a cyanide bath. However, the baths according to the present invention may also be employed with success in the direct acid copper plating process, that is, by subjecting the objects to be copperplated to a preliminary 3 treatment in an acid pickling bath with pickiling agents or wetting agents having a high inhibitor eifect and subsequently directly and without intermediate rinsing, transferring the objects into the acid copper electroplating bath.

The brightening agents according to the present inventionproduce metal electroplates which exhibit an excellent mirror brightening effect vwhicihmakes it unnecessary to subject the electroplated object to a subsequent polishing treatment.

The following examples are set forth to further illustrate the invention and to enable persons skilled in the art to better understand and practice they invention, and not intended to be limitative.

Example I 0.2 to 1.5 g./l. of N,N-diethyl-dithio-carbamic acid- S-benzylester-o-sodium sulfonate of the formula C H I are dissolved in an acid copper electroplating bath which contains 200 g./l. of crystallized copper sulfate, 60 g./l. of sulfuric acid, and 1 g./l of the addition product of 20 mols of ethylene oxide to 1 mol of a coconut fatty alcohol mixture. When brass or iron sheets are copper plated in this bath in a current density range of 0.5 to 8 amperes per dmf, ductile, pore-free, uniformly bright copper electroplates are obtained in a temperature range of 15 to 50 C. which completely level a 280 grain scratch with a copper deposit of 20 mu thick.

Example 11 When a bath of the same composition as that in Example I is modified with 0.2 to 1.5 g./l. of N,N-diethy1dithiocarbamic acid-S-benzylester-p-sodium sulfonate of the formula CgH5 S CgH5 as the brightening agent, equally good results as those in Example I are achieved.

Example III 0.1 to 1 g./1, of N,N-diethyl-dithiocarbamic acid-S- benzylester-o-sodium sulfon-ate are added to an acid zinc electroplating bath which contains 300 g./l, of zinc sulfate, g./l. of aluminum sulfate, and 20 g./l. of boric acid. The bath is operated in a pH range between 3 and 5 and produces bright, ductile, very fine grained zinc electrodeposits which adhere well to the iron surface in a current density range of 0.5 to 4 amperes per rim. with a temperature tolerance of to 45 C.

Example IV 0.5 to 1 g./l. of N,N-diethyl-dithiooarbamic acid-S- benzylester-p-sodium-sulfonate aredissolved in a nickel electroplating bath which contains 60 g./l. of nickel chloride, 220 g./l. of crystallized nickel sulfate, and 35 g./l. of boric acid. When operated at 60? C. and in current density ranges of 4 to 8 amperes per drn. this nickel electroplating bath produces bright electrodeposits.

Example V When an acid copper electroplating bath, which con tains 200 g./l. of copper sulfate and 60 g./l. of sulfuric acid, is modified with 10 mg./l. of N,N-l,5-pentamethyl 4 ene-dithio oarbamic acid-S- (m-methyl benzylester-sodiumsulfonate bright copper electroplates are obtained at room temperature in a current density range of 0.5 to 5 amperes per dmF.

Example VI When an acid copper electroplating bath, which contains 260 g./'l. of copper sulfate and 40 g./l. of sulfonic acid, is modified with 5 mg./1. of 3-oxa-l,5-pentamethylenerdithi ocarbamic acid-S-(p-methyl)-2-phenyl-ethylestersodium sulfonate bright electroplates are obtained in a current density range of l to 2.5 amperes pe-r dm. Above 2.5 amperes per dm. a certain increase in the fineness of the grain can also be observed. By addition of the reaction product of 1 mol of dooecyl alcohol and 6 mols of ethylene oxide in an amount of 2 g./l., which acts as a wetting agent, the brightening range can be broadened to 0.25 to 6 amperes per dm. The best brightening-effects are obtained ina temperature range of 23 to 29 C.

Example VII 30 mg./l. of 'S-phenyl-trithiocarbonic acid-S-(3,5-dimethyl) -benzyle ster-methyl-sodium-sulfonate S CH SO Na E I S--S-CH 1 to 5 mg./l. of n-butyl-xanthogenic acid-S-naphthylmethylester-sodium-sulfonate SO Na are added to an acid copper electroplating bath consist-v ing of 260 g./l. of copper sulfate and 40 g./l. of sulfuric acid. Operation of this bath produces bright copper electrodeposits in a current density range of 1 to 7 amperes per dmfi. The addition of a wetting agent for increasing the brightness or for broadeningthe current density range is not necessary.

Example IX 15 g./l. of the reaction product of sodium diethyldithiocarbamate and tetrapropylene benzene sodium sulfonate which is halogenated in the carbon chain C2H5 S Ni JsCH --so,Na C2415 are added to an acid copper electroplating bath containing 220 g./l. of copper sulfate and 60 g./l. of sulfuric acid. The bright copper electroplates obtained with the aid of this bath extend at room temperature from about 0.5 to 8 amperes per dm. The addition of a wetting agent is not required.

While we have set forth certain specific embodiments and preferred modes of practice of our invention, it will be understood that the invention is not limited thereby, and that various changes and modifications may be made Without departing from the spirit of the disclosure or the scope of the appended claims.

We claim:

1. An electroplating bath for producing bright and level electrodeposits of metals selected from the group consisting of copper, nickel and zinc comprising an acid aqueous solution of the metal to be electrodeposited and an additive compound of the formula wherein R is selected from the group consisting of aliphatic, cycloaliphatic and aromatic radicals, X is selected irom the group consisting of O-, S- and NR"-, R" is selected from the group consisting of hydrogen and aliphatic, cycloaliphatic and aromatic radicals and R and R" taken together with the nitrogen atom may form a heterocyclic radical, R is a bivalent hydrocarbon radical having an aryl group to which the SO G group is attached and G is selected from the group consisting of hydrogen and alkali metal; said additive being added in sufficient amount to obtain said bright and level electrodeposit.

2. An electroplating bath for producing bright and level electrodeposits of metals selected from the group consisting of copper, nickel and zinc comprising an acid aqueous solution of the metal to be electrodeposited and from 0.01 to g./l. of an additive compound of the formula wherein R is selected from the group consisting of aliphatic, cycloaliphatic and aromatic radicals, X is selected from the group consisting of O, and NR, R is selected from the group consisting of hydrogen and aliphatic, cycloaliphatic and aromatic radicalls and Rand R taken together with the nitrogen atom may form a 'heterocycli'c radical, R is a bivalent hydrocarbon radical having an aryl group to which the SO G group is attached and G is selected from the group consisting of hydrogen and alkali metal.

3. An electroplating process for producing bright and level electrodeposits of metals selected from the group consisting of copper, nickel and zinc comprising electrodepositing the said metals from a bath comprising an acid aqueous solution of the metal to be electrodeposited in the presence of an additive compound of the formula wherein R is selected from the group consisting of aliphatic, cycloaliphatic and aromatic radicals, X is selected from the group consisting of O-, -S and -NR", R is selected from the group consisting of hydrogen and aliphatic, cycloaliphatic and aromatic radicals and R and R" taken together with the nitrogen atom may form a heterocyclic radical, R is a bivalent hydrocarbon radical having an aryl group to which the SO G group is attached and G is selected from the group consisting of hydrogen and alkali metal.

4. An electroplating process for producing bright and level electrodeposits of metals selected from the group consisting of copper, nickel and Zinc, comprising electrodepositing the said metals from a bath comprising an I acid aqueous solution of the metal to be electrodeposited 6 in the presence of from 0.01 to 20 g./l. of an additive compound of the formula wherein R is selected from the group consisting of allphatic, cycloaliphatic and aromatic radicals, X is selected from the group consisting of O, S- and -NR"-, R" is selected from the group consisting of hydrogen and aliphatic, cycloaliphatic and aromatic radicals and R and R taken together with the nitrogen atom may form a heterocyclic radical, R is a bivalent hydrocarbon radical having an aryl group to which the SO G groups is attached and G is selected from the groupconsisting of hydrogen and alkali metal.

5. An electroplating bath for producing bright and level electrodeposits of metals selected from the group consisting of copper, nickel and zinc comprising an acid aqueous solution of the metal to be electrodeposited and from 0.01 to 20 g./l. of an additive compound having a structural formula as follows:

C H5 S N-ll CgHs SO Na 6. An electroplating bath for producing bright and level electrodeposits of metals selected from the group consisting of copper, nickel, and Zinc comprising an acid aqueous solution of the metal to .be electrodeposited and from 0.01 to 20 g./l. of an additive compoundhaving a structural formula as follows:

8. An electroplating bath"for'producing bright and level electrodeposits of metals selected from the group consisting of copper, nickel, and zinc comprising an acid aqueous solution of the metal to be electrodeposited and from 0.01 to 20 g./l. of an additive compound having a structural formula as follows:

C z-CH2 S ll O\ N SCH2CH2 CH3 CHPCHI soaNa 9. An electroplating bath for producing bright and level electrodeposits of metals selected from the group consisting of copper, nickel, and Zinc comprising an acid aqueous solution of the metal to be electrodeposited and from 0.01 to 20 g./l. of an additive compound having a structural formula as follows:

10. An electroplating bath for producing bright and level electrodeposits of metals selected from the group consisting of copper, nickel, and zinc comprising an acid aqueous solution of the metal to be electrodeposited CH3 SO NB r 7 and from 0.01 to g./l. of an additive compound having a structural formula as follows:

11. An electroplating bath for producing bright and level electrodeposits of metals selected from the group consisting of copper, nickel, and zinc comprising an acid aqueous solution of the metal to be electrodeposited and from 0.01 to 20 g./l. of an additive compound having a structural formula as follows:

12. An electroplating process for producing bright and level electrodeposits of metals selected from the group consisting of copper, nickel, and zinc comprising electrodepositing the metals from a bath comprising an acid aqueous solution of the metal to be electrodeposited and from 0.01 to 20 g./l. of an additive compound having a structural formula as follows:

13. A11 electroplating process for producing bright and level electrodeposits of metals selected from the group consisting of copper. nickel, and zinc comprising electrodepositing the metals from a bath comprising an acid aqueous solution of the metal to be electrodeposited in the presence of from 0.01 to 20 g./l. of an additive compound having a structural formula as follows:

14. An electroplating process for producing bright and level electrodeposits of metals selected from the group consisting of copper, nickel, and zinc comprising electrodepositing the metals from a bath comprising an acid aqueous solution of the metal to be electrodeposited in the presence of from 0.01 to 20 g./l. of an additive compound having a structural formula as follows:

15. An electroplating process for producing bright and level electrodeposits of metals selected from the group consisting of copper, nickel, and zinc comprising electrodepositing the metals from a bath comprising an acid aqueous solution of the metal to be electrodeposited in the presence of from 0.01 to 20 g./l. of an additive com pound having a structural formula as follows:

16. An electroplating process for producing bright and level electrodeposits of metals selected from the group consisting of copper, nickel, and zinc comprising electrodepositing the metalsfrom a bath comprising an acid in the presence from 0.01 to 20 g./l. of ,an additive com: pound having a structural formula as follows:

CH SOQNB S V I 17. An electroplating process for producing bright and level electrodeposits of metals selected from the group consisting of copper, nickel, and zinc comprising electrodepositing the metals from a bath comprising an acid aqueous solution of the metal to be electrodeposited in the presence of from 0.01 to 20 g./-l. of an additive compound having a structural formula as follows:

18. An electroplating process for producing bright and level electrodeposits of metals selected from the group consisting of copper, nickel, and zinc comprising electrodepositing the metals from a bath comprising an acid aqueous solution of the metal to be electrodepos-ited in the presence of from 0.01 to 20 g./l. of an additive compound having a structural formula as follows:

ca s S References Cited by the Examiner UNITED STATES PATENTS JOHN H. MACK, Primary Examiner.-

G. KAPLAN, Assistant Examiner. 

1. AN ELECTROPLATING BATH FOR PRODUCING BRIGHT AND LEVEL ELECTRODEPOSITS OF METALS SELECTED FROM THE GROUP CONSISTING OF COPPER, NICKEL AND ZINC COMPRISING AN ACID AQUEOUS SOLUTION OF THE METAL TO BE ELECTRODEPOSITED AND AN ADDITIVE COMPOUND OF THE FORMULA 